The invention occurred relative to resin cartridges for sealants and caulking compounds, often called "caulkers" in the art. Caulkers have a closure member that serves as a plunger to expel the contents on demand, and various circumstances can cause the plunger to back out of a fully loaded caulker to waste the contents and spoil other caulkers in the same carton. Thermal expansion of the contents, entrapped air, or gasses produced by reactions with the contents can back the plunger out, and this mishap can be facilitated by improper placement or dimensioning of the plunger relative to the caulker. The problem is substantial enough to warrant a simple solution, and yet none has been satisfactory in the art.
The invention aims at a simple, economical, and reliable way of providing an interlock between the inside of a cylinder and a member fitting into the inside of the cylinder, not only as applied to the barrels and closure plungers of caulkers, but possibly also to mailing tubes and other uses where a simple and reliable interlock is desired between a cylinder and an internal member.